Common techniques for detecting pipeline defects include magnetic flux leakage testing, eddy current testing and so on. The magnetic flux leakage testing has relatively high detection precision, but needs a magnetizer during detection, a detection device used has a relatively complicated structure, and the magnetizer (like a permanent magnet) may have an absorption effect on the pipeline, thereby hindering the operation of the detector in the pipeline. The eddy current testing employs an eddy-current coil as an excitation source and has a simpler structure, but it achieves measurement of an eddy current change at a defect through an induction coil, thus obtaining less defect information and only achieving an approximate location of the defect and simple categorization.
In the related art, for example, “Long-distance Pipeline Defect Positioning Method and Positioning System” (ZL20071018 7426.2) adopts an eddy-current testing device to implement detection of a pipeline defect, but can only determine a location of the pipeline defect without imaging the defect; “In-pipeline Detector Signal Activating and Collecting Device and Pipeline Defect Detection Method” (ZL201410352876.2) provides a device for activating and collecting an in-pipeline detector signal and a method for detecting a pipeline defect, in which the method can only determine the type of the defect, such as an internal defect, an external defect, a crack defect and so on, but cannot perform inversion imaging of the defect. It can be seen that the existing eddy-current testing device has the advantage of simple structure but obtains less defect information, and can hardly achieve high-precision detection and imaging of the pipeline defect based on the insufficient detection information.